As one of connection forms to an internet, a wireless LAN (Local Area network) is widely propagated. The wireless LAN, which is different from a wired LAN, is one form of the LAN which can be connected to a network such as the internet without using a LAN cable. The wireless LAN is promoted to be standardized by the IEEE802.11. At present, there are standards of the IEEE802.11b, IEEE802.11g and IEEE802.11a.
The IEEE802.11b is the standard for carrying out a communication at a speed of about 11 Mbps at maximum by using a radio wave of a frequency band of 2.4 GHz. The IEEE802.11g is the standard for carrying out a communication at a speed of about 54 Mbps at maximum by using a radio wave of a frequency band of 2.4 GHz. The IEEE802.11a is the standard for carrying out a communication at a speed of about 54 Mbps at maximum by using a radio wave of a frequency band of 5.2 GHz. A device using the wireless LAN according to these standards constructs the network, so that the device can carry out a communication using the wireless LAN.
A wireless LAN device to be mounted on a vehicle disclosed in Patent Document 1 is known as one example of wireless LAN devices that a device based on the standard of such a wireless LAN is applied to a device to be mounted on a vehicle to carry out a wireless communication between the vehicle on which the device to be mounted on the vehicle is mounted and an external wireless base station.
Here, a structure and an operation of the wireless LAN device to be mounted on the vehicle of the Patent Document 1 will be described below by referring to FIG. 12 to FIG. 14. FIG. 12 is a block diagram showing an inner structure of the wireless LAN device 20 to be mounted on the vehicle. FIG. 13 is a flowchart for explaining a connecting procedure to a wireless LAN access point as a target for communication of the wireless LAN device 20 to be mounted on the vehicle. FIG. 14 is an explanatory view showing one example of a peripheral access point list.
In FIG. 12, the wireless LAN device 20 to be mounted on the vehicle includes, a system MPU21, a GPS receiver 22, a gyro-sensor 23a, a vehicle speed pulse sensor 23b, an HDD 24a, a DVD-ROM drive 24b, an image processing section 25, a display 26, an audio processing section 27, a microphone 28a, a speaker 28b, a control panel 29 and a wireless LAN module 30.
The operation of the wireless LAN 20 to be mounted on the vehicle will be described below. In FIG. 13, the wireless LAN device 20 to be mounted on the vehicle initially searches received signal intensity (RSSI) of a beacon signal broadcast from a wireless LAN access point (S401). The wireless LAN device 20 to be mounted on the vehicle forms an RSSI list of the wireless LAN access points existing in the periphery of a present position of the vehicle of its own (S402). The wireless LAN device 20 to be mounted on the vehicle forms the RSSI list to specify the wireless LAN access point available at this time.
Then, the wireless LAN device 20 to be mounted on the vehicle reads the peripheral access point list of the wireless LAN access points existing in the periphery of the present position of the vehicle of its own (S403). The peripheral access point list is previously formed and held by the wireless LAN device 20 to be mounted on the vehicle and periodically updated to the latest information.
FIG. 14 is a diagram showing one example of the peripheral access point list. In this example, “No.”, “SSID”, “position information” of the wireless LAN access point and “profile” are shown. The profile is a setting file including information necessary for connection to the wireless LAN access point. For instance, an MAC address, an encryption system and an encryption key thereof or the like are included.
The encryption system includes WEP, TKIP, AES or the like. The profile does not need to be previously coordinated with all the wireless LAN access points registered in the data base of the HDD 24a or the DVD-ROM drive 24b. 
In FIG. 13, the wireless LAN device 20 to be mounted on the vehicle filters the wireless LAN access points in the peripheral access point list by using the RSSI list (S404). The RSSI list is a list of actually operating wireless LAN access points. However, the peripheral access point list is a list on a data base to the end. Accordingly, it is not obvious that the position information includes even information as to whether or not the wireless LAN access points are actually located or whether or not the wireless access points actually operate. Thus, the wireless LAN device 20 to be mounted on the vehicle puts the peripheral access point list on the RSSI list, so that the wireless LAN device 20 to be mounted on the vehicle can list up only the wireless LAN access points which can be actually connected.
The wireless LAN device 20 to be mounted on the vehicle selects the wireless LAN access point having the profile from the peripheral access point list in which a filtering process is finished (S405) and tries to carry out a network connection to the wireless LAN access point (S406). When the connection is established, the wireless LAN device 20 to be mounted on the vehicle monitors a connection state and a distance to the access point (S407), and when the connection is hardly maintained, the wireless LAN device 20 to be mounted on the vehicle resumes the above-described series of connecting procedure (S407, YES).
In such a way, the wireless LAN device 20 to be mounted on the vehicle can operate so as to cooperate with a car navigation device which can specify the preset position of the vehicle. Further, the wireless LAN device 20 to be mounted on the vehicle can simply set profile information necessary for connecting with the wireless LAN access point and connect with the wireless LAN access point.